Small Dent in Mouthpiece

I noticed today that I have a small dent in the stem of the mouthpiece (thin end). This appears to make the hole in the mouthpiece slightly uncircular.

I guess I dropped my mouthpiece somewhere although I don't remember it?! What I really am concerned about is the effect it will have. I'm thinking that it will have a large effect on tone quality and even note accuracy, am I right here and should I get a new mouthpiece or does a small dent really have no impact?

As long as the mouthpiece still fits in the lead pipe and it doesn't leak, I should think that it wouldn't have a noticeable impact on your playing unless you are extremely picky. My mouthpiece isn't exactly circular on the end either, and I have no qualms about it. Although it might be a good idea to take it to somebody who can properly straighten it out; it would fix the minor problem you are encountering and still hopefully be significantly cheaper than a new mouthpiece altogether.

The mouthpiece is designed to have the air flow a certain particular way. With a 'dent' in the end it will affect something and as a less advanced player you might not notice what it is. You do have to buy oil and grease and such for your horn eventually. I would suggest going to your local repair person and buy some oil and whatever else you need and ask if they can fix that for you. If you are buying supplies I wouldn't charge you anything. If you were not buying anything I'd charge you $2. It's a very simple and very quick process that consists of putting the mouthpiece on a steel mandrell - it takes a professional about 5 or 10 seconds to do. I think every Band director should have a small set of mandrells in their office if not take it over to your schools machine shop and see if the shop teacher will straighten for you.

Ah ok so it will have some effect on my playing and i should get it fixed. That's good because I was thinking I would have to buy a new mouthpiece and at £60 + dropping my mouthpiece would prove quite costly!!

As JOhnlovemusic said, you can have it done for free, or almost. Before last summer I went to a technician, because I was playing a borrowed horn and I had to return it (its owner needed it). When I was given it, it had many dents, and I thought that I would have them taken away in appreciation of his having lent it to me. I left the horn at the shop, and kept the mouthpiece so as to be able to practice without the horn. When I went to fetch it three days later, the technician asked me whether I had my mouthpiece with me. I gave it to him, and in about a minute he brought it back without the two dents it had like the one you've described, and clean. I didn't even asked for it; ha made it spontaneously. Of course, I was going to pay much money for the other job, but anyway I thought it was very nice of him.

I am curious as to whether or not it is possible to easily change the taper of the mouthpiece. Mine does not fit perfectly into the lead pipe on my horn and I would like to know if it's both a good idea and relatively easy to do to change the taper to fit my horn better.

Technically yes, it is easy to change the taper of the mouthpiece - but to do it proeprly takes skill, experience, and the correct tool(s). If the mouthpiece does not fit properly it might not be the mouthpiece, it could be a worn out leadpipe reciever; or it could be a eropean shank/american shank going into the opposite style reciever.

It is not a good idea to change the taper. Doing so changes how deep the mouthpiece sits in the leadpipe which will directly affect your tone, articulations, and response.